My favorite is Tennant, with Smith as a close second. I've only seen two episodes from before 2005 (one was in black and white with the first Doctor), so I can't really say anything about the older Doctors.

My favorite is definitely Tennant, followed by Smith. But that doesn't mean I didn't like Eccleston, because I thought he was "FANTASTIC". I guess he just didn't have enough seasons (Only one... v_v) to really get me hooked.